1. Field of the Invention
The present invention relates to a buttonhole sewing machine, and particularly to a buttonhole sewing machine which is compact in size and improved in operation, and which sews beautifully finished buttonholes with no disorder in the stitches.
2. Description of the Prior Art
The conventional buttonhole sewing technique utilizes an elongated slit s (FIG. 6a) which is terminated at its one end with an eyelet hole e, and stitches a and a' are formed in parallel at the opposite sides of the slit s and perpendicular to the slit s, the stitches a and a' being connected with each other by radial stitches b and offset stitches c and c', the eyelet hole being surrounded by these stitches c, c', and b. On the other hand, when no eyelet hole is formed, the stitches a and a' are connected through the radial stitches b (FIG. 6b), so as to provide a so-called straight buttonhole sewing.
Such buttonhole sewing machines have a long history of development, and various types have been developed and disclosed, for example, in the following:
______________________________________ a - 1 Japanese Patent No. 25276 2 Japanese Patent No. 26968 3 Japanese Patent No. 36153 b Japanese Patent No. 94060 c - 1 Japanese Patent No. 118369 2 Japanese Patent No. 118405 3 Japanese Patent No. 123686 4 Japanese Patent No. 135034 5 Japanese Patent Publication No. 1125/1955 d Japanese Patent Publication No. 536/1950 e Japanese Patent Publication No. 3541/1953 f Japanese Patent Publication No. 27462/1972 g - 1 Japanese Patent Publication No. 730/1951 2 Japanese Patent Publication No. 4886/1951 3 Japanese Patent Publication No. 2893/1952 4 Japanese Patent Publication No. 1126/1955 5 Japanese Patent Publication No. 5834/1955 U.S. Pat. No. 2,174,294 U.S. Pat. No. 2,301,797 U.S. Pat. No. 1,941,620 U.S. Pat. No. 1,981,119 U.S. Pat. No. 1,988,460 U.S. Pat. No. 1,991,627 ______________________________________
In general, in the prior art buttonhole sewing machines, an electric motor of 1/2-1/4 HP has been employed to transmit power to a cutting operation mechanism and a work clamp feeding mechanism through one belt drive system and to a stitch forming mechanism through another belt drive system, and therefore the sewing machines have been large in size and heavy in weight (about 100 Kg), making them difficult to carry. Further, because of their large size as well as heavy weight, energy consumption has been undesirably high.
Although those sewing machines have been designed as precision machines, their operation was not so good and adjustment required very highly technical special knowledge, and therefore they have been used mainly in sewing or needle-work makers or the like only when the expense and maintenance of the equipment of those sewing machines could be afforded. Accordingly, buttonhole sewing machines could not be afforded in tailor shops, small entity dressmaking workshops, etc.
The prior art encountered difficulties in that different types of buttonhole sewing machines were required stitching for different techniques such as so-called before-cutting (after cutting a buttonhole stitches are formed), after-cutting (after stitches are formed a buttonhole is cut), etc.